Conversion of 2-chloro-1,1,1,2-tetrafluoropropane to 2,3,3,3-tetrafluoropropene

ABSTRACT

Described is a method for producing fluoropropenes of formula CF 3 CX═CX 2  wherein each X is F or H, at least one X is H, and at least one X is F, comprising pyrolyzing a hydrofluorochloropropane of formula CF 3 CXYCX 2 Y, wherein each X is F or H, at least one X is H, and at least one X is F, and one Y is Cl and the other Y is H, in the gas-phase in a reaction vessel, maintained at a temperature high enough to effect the pyrolysis of said hydrofluorochloropropane to said fluoropropene, wherein the selectivity for the production of the fluoropropene is at least 80%, in the absence of a catalyst

CROSS REFERENCE(S) TO RELATED APPLICATION(S)

This application is a continuation-in-part of U.S. application Ser. No.12/605,573, filed Oct. 26, 2009, which claims the benefit of priority ofU.S. Provisional Applications 61/108,585, filed Oct. 27, 2008, and61/121,248, filed Dec. 10, 2008.

BACKGROUND INFORMATION

1. Field of the Disclosure

This disclosure relates in general to methods of synthesis offluorinated olefins.

2. Description of the Related Art

The fluorocarbon industry has been working for the past few decades tofind replacement refrigerants for the ozone depletingchlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) beingphased out as a result of the Montreal Protocol. The solution for manyapplications has been the commercialization of hydrofluorocarbon (HFC)compounds for use as refrigerants, solvents, fire extinguishing agents,blowing agents and propellants. These new compounds, such as HFCrefrigerants, HFC-134a and HFC-125 being the most widely used at thistime, have zero ozone depletion potential and thus are not affected bythe current regulatory phase-out as a result of the Montreal Protocol.

In addition to ozone depleting concerns, global warming is anotherenvironmental concern in many of these applications. Thus, there is aneed for compositions that meet both low ozone depletion standards aswell as having low global warming potentials. Certain hydrofluoroolefinsare believed to meet both goals. Thus there is a need for manufacturingprocesses that provide halogenated hydrocarbons and fluoroolefins thatcontain no chlorine that also have a low global warming potential.

SUMMARY

Described is a method for producing a fluoropropene of formulaCF₃CF═CH₂, comprising pyrolyzing a hydrofluorochloropropane of formulaCF₃CFClCH₃, in the gas-phase in a reaction vessel, maintained at atemperature of from about 400° C. to 700° C., wherein the selectivityfor the production of the fluoropropene is at least 80%, in the absenceof a catalyst.

The foregoing general description and the following detailed descriptionare exemplary and explanatory only and are not restrictive of theinvention, as defined in the appended claims.

DETAILED DESCRIPTION

Described is a method for producing fluoropropenes of formula CF₃CX═CX₂wherein each X is F or H, at least one X is H, and at least one X is F,comprising pyrolyzing a hydrofluorochloropropane of formula CF₃CXYCX₂Y,wherein each X is F or H, at least one X is H, and at least one X is F,and one Y is Cl and the other Y is H, in the gas-phase in a reactionvessel, maintained at a temperature high enough to effect the pyrolysisof said hydrofluorochloropropane to said fluoropropene, wherein theselectivity for the production of the fluoropropene is at least 80%, inthe absence of a catalyst.

Many aspects and embodiments have been described above and are merelyexemplary and not limiting. After reading this specification, skilledartisans appreciate that other aspects and embodiments are possiblewithout departing from the scope of the invention.

Other features and benefits of any one or more of the embodiments willbe apparent from the following detailed description, and from theclaims.

Before addressing details of embodiments described below, some terms aredefined or clarified.

As used herein, the terms pyrolyzing and pyrolysis refer to thedecomposition or breaking down of a material or compound due to heat inthe absence of oxygen or any other reagents.

As used herein, reaction vessel refers to any vessel in which thereaction may be performed in either a batchwise mode, or in a continuousmode. Suitable vessels include batch reactor vessels, or tubularreactors.

In one embodiment, the reaction vessel is comprised of materials whichare resistant to corrosion including stainless steel, Hastelloy,Inconel, Inconel 600, Inconel 625, Hastelloy C, Hastelloy B1 HastelloyB2, Monel, gold, or gold-lined, quartz or nickel.

As used herein, percent selectivity is defined as the weight of adesired product formed, as a fraction of the total amount of theproducts formed in the reaction, and excluding the startingchlorofluorocarbon.

As used herein, percent conversion is defined as 100%, less the weightpercent of starting hydrofluorochloropropane in the effluent from thereaction vessel.

The hydrochlorofluoropropane described herein has the formulaCF₃CXYCX₂Y, wherein each X is F or H, at least one X is H, and at leastone X is F, and one Y is Cl and the other Y is H. A fluoropropene asdescribed herein has the formula CF₃CX═CX₂ wherein each X is F or H, atleast one X is H, and at least one X is F. Representativehydrochlorofluoropropanes include 1,1,1,2-tetrafluoro-2-chloropropane,1,1,1,2-tetrafluoro-3-chloropropane,1,1,1,3-tetrafluoro-2-chloropropane,1,1,1,3-tetrafluoro-3-chloropropane,1,1,1,2,3-pentafluoro-2-chloropropane,1,1,1,2,3-pentafluoro-3-chloropropane,1,1,1,3,3-pentafluoro-2-chloropropane and1,1,1,3,3-pentafluoro-3-chloropropane.

Representative fluoropropenes include 2,3,3,3-tetrafluoropropene,1,3,3,3-tetrafluoropropene, 1,2,3,3,3-pentafluoropropene and1,1,3,3,3-pentafluoropropene.

In one embodiment, the hydrochlorofluoropropane is1,1,1,2-tetrafluoro-2-chloropropane and the fluoropropene is2,3,3,3-tetrafluoropropene. In another embodiment, thehydrochlorofluoropropane is 1,1,1,2-tetrafluoro-3-chloropropane and thefluoropropene is 2,3,3,3-tetrafluoropropene. In yet another embodiment,the hydrochlorofluoropropane is 1,1,1,3-tetrafluoro-2-chloropropane andthe fluoropropene is 1,3,3,3-tetrafluoropropene. In yet anotherembodiment, the hydrochlorofluoropropane is1,1,1,3-tetrafluoro-3-chloropropane and the fluoropropene is1,3,3,3-tetrafluoropropene. In yet another embodiment, thehydrochlorofluoropropane is 1,1,1,2,3-pentafluoro-2-chloropropane andthe fluoropropene is 1,2,3,3,3-pentafluoropropene. In yet anotherembodiment, the hydrochlorofluoropropane is1,1,1,2,3-pentafluoro-3-chloropropane and the fluoropropene is1,2,3,3,3-pentafluoropropene. In yet another embodiment, thehydrochlorofluoropropane is 1,1,1,3,3-pentafluoro-2-chloropropane andthe fluoropropene is 1,1,3,3,3-pentafluoropropene. In yet anotherembodiment, the hydrochlorofluoropropane is1,1,1,3,3-pentafluoro-3-chloropropane and the fluoropropene is1,1,3,3,3-pentafluoropropene.

In one embodiment, fluoropropenes are prepared by thermaldehydrochlorination of hydrochlorofluoropropanes. This reaction occursselectively, in the absence of a catalyst. In one embodiment, ahydrochlorofluoropropane is introduced into a reaction vessel whereinthe temperature is maintained at a temperature high enough to effect thethermal dehydrochlorination of the hydrochlorofluoropropane. In oneembodiment, the temperature is high enough to effect the thermaldehydrochlorination to a percent conversion of at least 20%. In anotherembodiment, the temperature is high enough to effect the thermaldehydrochlorination of the hydrochlorofluoropropane to a percentconversion of at least 50%. In another embodiment, the temperature ishigh enough to effect the thermal dehydrochlorination of thehydrochlorofluoropropane to a percent conversion of at least 65%. In yetanother embodiment, the temperature is high enough to effect the thermaldehydrochlorination of the hydrochlorofluoropropane to a percentconversion of at least 80%. In yet another embodiment, the temperatureis high enough to effect the thermal dehydrochlorination of thehydrochlorofluoropropane to a percent conversion of at least 70% for atleast 12 hours of continuous operation.

In one embodiment, the hydrochlorofluoropropane is introduced into areaction vessel wherein the temperature is maintained at a temperaturein the range of from about 400° C. to about 700° C. In anotherembodiment, the temperature of the reaction vessel is maintained in therange from about 400° C. to about 600° C. In yet another embodiment, thetemperature of the reaction vessel is maintained at a temperature highenough to effect the the pyrolysis of the hydrochlorofluoropropane tofluoropropene with a selectivity of 80% or greater. In yet anotherembodiment, the temperature of the reaction vessel is maintained at atemperature high enough to effect the pyrolysis of thehydrochlorofluoropropane to the fluoropropene with a selectivity of 85%or greater.

In one embodiment, the reaction vessel is comprised of materials whichare resistant to corrosion. In one embodiment, these materials comprisealloys, such as stainless steel, Hastelloy, Inconel, Inconel 600,Inconel 625, Hastelloy C, Hastelloy B1 Hastelloy B2, Monel, gold, orgold-lined, quartz or nickel.

In one embodiment, the hydrochlorofluoropropane is preheated in avaporizer to a temperature of from about 30° C. to about 100° C. Inanother embodiment, the hydrochlorofluoropropane is preheated in avaporizer to a temperature of from about 30° C. to about 80° C.

In some embodiments, an inert diluent gas is used as a carrier gas forthe hydrochlorofluoropropane. In one embodiment, the carrier gas isselected from nitrogen, argon, helium or carbon dioxide.

In one embodiment the reaction vessel is of a design commonly referredto as a shell and tube reactor. In one embodiment, heat input into thereaction is provided through the use of a superheated diluent gas toprovide sufficient heat input into the reactor and incoming rawmaterials.

The reaction pressure can be subatmpospheric, atmospheric orsuperatmostpheric. In one embodiment, the reaction is conducted at apressure of from 14 psig to about 100 psig. In another embodiment, thereaction is conducted at a pressure of from 14 psig to about 60 psig. Inyet another embodiment, the reaction is conducted at a pressure of from40 psig to about 85 psig. In yet another embodiment, the reaction isconducted at a pressure of from 50 psig to 75 psig.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

Also, use of “a” or “an” are employed to describe elements andcomponents described herein. This is done merely for convenience and togive a general sense of the scope of the invention. This descriptionshould be read to include one or at least one and the singular alsoincludes the plural unless it is obvious that it is meant otherwise.

Group numbers corresponding to columns within the Periodic Table of theelements use the “New Notation” convention as seen in the CRC Handbookof Chemistry and Physics, 81^(st) Edition (2000-2001).

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of embodiments of the present invention, suitablemethods and materials are described below. All publications, patentapplications, patents, and other references mentioned herein areincorporated by reference in their entirety, unless a particular passageis cited. In case of conflict, the present specification, includingdefinitions, will control. In addition, the materials, methods, andexamples are illustrative only and not intended to be limiting.

EXAMPLES

The concepts described herein will be further described in the followingexamples, which do not limit the scope of the invention described in theclaims.

Legend

HFC-244bb is 2-chloro-1,1,1,2-tetrafluoropropaneHFO-1234yf is 2,3,3,3-tetrafluoropropeneHCFO-1233xf is 2-chloro-3,3,3-trifluoropropene

Example 1

Example 1 demonstrates the conversion of2-chloro-1,1,1,2-tetrafluoropropane to 2,3,3,3-tetrafluoropropene in theabsence of a catalyst.

An empty inconel tube (½ inch OD) with a heated zone of about 12 incheswas heated to a temperature between 500° C. and 626° C., and HFC-244bbwas fed at 0.52 ml/hour through a vaporizer set at 40° C. using a N₂sweep of 2.4 sccm (4.0×10⁻⁸ m³). The reactor effluent was analyzed usingan on-line GCMS, with the results being reported in mole percent.Results for percent conversion, percent selectivity, and operatingtemperature are reported in Table 1, below.

TABLE 1 Conversion Selectivity Selectivity Temp ° C. of 244bb to 1234yfto 1233xf 500 16.2% 80% 8% 550 65.4% 88% 2% 574 86.4% 88% 2% 601 99.6%85% <1%  626 99.8% 83% 1%

Example 2

Example 2 demonstrates the conversion of2-chloro-1,1,1,2-tetrafluoropropane to 2,3,3,3-tetrafluoropropene in theabsence of a catalyst.

An empty inconel tube (½ inch OD) with a heated zone of about 12 incheswas heated to 575° C., and HFC-244bb was fed at 0.35 ml/hour through avaporizer set at 40° C. using a N₂ sweep of 3.6 sccm (6.0×10⁻⁸ m³). Thereactor was operated for a total of 19 hours continuously, and sampleswere taken periodically and analyzed to determine % conversion ofHFC-244bb, and selectivity to HFO-1234yf. The reactor effluent wasanalyzed using an on-line GCMS, and the data in Table 2 below is anaverage of at least two on-line injections at a given condition; thepercentages are mole percent. The data in Table 2 show the performanceof this reaction to make HFO-1234yf via HCl elimination over the periodof 19 hours of operation.

TABLE 2 Conversion Selectivity Selectivity Hours of 244bb to 1234yf to1233xf 3 80% 84%  6% 4 75% 80% 9.7%  8 81% 72% 17% 12 81% 70% 20% 15 82%78% 14% 19 85% 73% 19.6% 

Example 3

Example 3 demonstrates the conversion of2-chloro-1,1,1,2-tetrafluoropropane to 2,3,3,3-tetrafluoropropene in theabsence of a catalyst in a gold-lined tube.

An empty gold-lined tube (½ inch OD) with a heated zone of about 12inches was heated to a temperature about 550° C., and HFC-244bb was fedat 0.75 ml/hour through a vaporizer set at 40° C. using a N₂ sweep of3.75 sccm (6.25×10⁻⁸ m³). The reactor effluent was analyzed using anon-line GCMS, with the results being reported in mole percent. Resultsfor percent conversion, percent selectivity, and operating temperatureare reported in Table 3, below.

TABLE 3 Conversion Selectivity Selectivity Temp ° C. of 244bb to 1234yfto 1233xf 550 72% 94% 2%

Example 4

Example 4 shows the conversion of 2-chloro-1,1,1,2-tetrafluoropropane to2,3,3,3-tetrafluoropropene in the absence of a catalyst at 480° C.

A mixture of 99% of 244bb and 1% of 1233xf was passed through a ½″×12″(ID 0.334″) Inconel 625 tube with flow rates of 2.4 ml/hr, 1.2 ml/hr,0.8 ml/hr and 0.4 ml/hr at 480° C. at 1 atmosphere pressure. The streamfrom the reactor was analyzed by GC and GC-MS. The result of the test islisted in Table 4 below. The reaction shows high selectivity to 1234yfand low selectivity to 1233xf.

TABLE 4 Flow rate 2.4 ml/hr 1.2 ml/hr 0.8 ml/hr 0.4 ml/hr % 1234yf 22 3138 51 % 244bb 76 67 59 47 % 1233xf 1 1 1 1

Example 5

Example 5 illustrates long reactor life in the dehydrochlorination of244bb in the absence of hydrogen fluoride.

A mixture of 99% of 244bb and 1% of 1233xf was passed through a ½″×12″(ID 0.334″) Inconel 625 tube for dehydrochlorination at a flow rate of 1ml/hr. The 244bb used in this reaction was scrubbed by deionized waterand contained no detectable HF. The stream from the reactor was analyzedby GC and GC-MS. The result of the test is listed in Table 5 below. Thereaction shows high selectivity to 1234yf and low selectivity to 1233xfout to 2000 hours of operation.

TABLE 5 Time (hr) % 1234yf % 1233xf % 244bb Temp (° C.) 600 24.1 1.074.6 440 1500 29.0 1.1 69.5 445 2002 24.0 1.1 74.6 446

Example 6

This example demonstrates the conversion of2-chloro-1,1,1,2-tetrafluoropropane to 2,3,3,3-tetrafluoropropene in theabsence of a catalyst at 435° C. with 50 psig back pressure.

An empty Inconel tube (½ inch OD, 0.334″ ID) with a heated zone of about12 inches was heated to 435° C., and HFC-244bb was fed at 1 ml/hourthrough a vaporizer set at 40° C. The reactor was operated at 50 psigbackpressure and at this condition for 280 hours continuously, andsamples were taken periodically and analyzed to determine % conversionof HFC-244bb, and selectivity to HFO-1234yf. The reactor effluent wasanalyzed using an on-line GCMS, and the data were listed in Table 6below; the percentages are mole percent. The data in Table 6 below showthe performance of this reaction to make HFO-1234yf via HCl eliminationover the period of 283 hours of operation.

TABLE 6 Conversion Selectivity Selectivity Back pressure Hours of 244bbto 1234yf to 1233xf Psig 2 25.90% 98.21% 0.20% 49.9 40 24.22% 98.18%0.20% 50.9 80 23.02% 98.18% 0.18% 49.9 120 24.54% 98.21% 0.17% 50.9 20023.06% 98.22% 0.20% 49.9 280 23.00% 98.44% 0.44% 49.5

Example 7

This example demonstrates the conversion of2-chloro-1,1,1,2-tetrafluoropropane to 2,3,3,3-tetrafluoropropene in theabsence of a catalyst at 460° C. with 1.2 psig and 50 psig backpressure.

An empty Inconel tube (½ inch OD, 0.334″ ID) with a heated zone of about12 inches was heated to 460° C., and HFC-244bb was fed at 1.2 ml/hourthrough a vaporizer set at 40° C. The reactor was operated at atmospherepressure for 4 hours and then at 50 psig backpressure for 4 hr, andsamples were taken periodically and analyzed to determine % conversionof HFC-244bb, and selectivity to HFO-1234yf. The reactor effluent wasanalyzed using an on-line GCMS, and the data were listed in Table below;the percentages are mole percent. The data in Table 7 below show theperformance of this reaction to make HFO-1234yf via HCl elimination at460° C.

TABLE 7 Conversion Selectivity Selectivity Back pressure Hours of 244bbto 1234yf to 1233xf (Psig) 1 14.36% 92.09% 4.47% 1.210 2 10.45% 93.23%3.23% 1.210 3 9.26% 93.04% 3.02% 1.210 4 8.65% 92.80% 3.00% 1.210 529.39% 95.81% 1.14% 46.460 6 24.03% 96.78% 0.94% 47.470 7 25.16% 96.92%0.80% 50.490 8 26.49% 97.05% 0.73% 50.490

Example 8

This example demonstrates the conversion of2-chloro-1,1,1,2-tetrafluoropropane to 2,3,3,3-tetrafluoropropene in theabsence of a catalyst at 480° C. with 1.2 psig and 50 psig backpressure.

An empty Inconel tube (½ inch OD, 0.334″ ID) with a heated zone of about12 inches was heated to 480° C., and HFC-244bb was fed at 1.2 ml/hourthrough a vaporizer set at 40° C. The reactor was operated at atmospherepressure for 5 hours and then at 50 psig backpressure for 4 hr, andsamples were taken periodically and analyzed to determine % conversionof HFC-244bb, and selectivity to HFO-1234yf. The reactor effluent wasanalyzed using an on-line GCMS, and the data were listed in Table below;the percentages are mole percent. The data in Table 8 below show theperformance of this reaction to make HFO-1234yf via HCl elimination at480° C.

TABLE 8 Conversion Selectivity Selectivity Back pressure Hours of 244bbto 1234yf to 1233xf (Psig) 1 22.96% 96.50% 1.21% 1.239 2 22.80% 97.06%0.92% 1.239 3 22.23% 97.10% 0.82% 1.239 4 23.43% 97.19% 0.74% 1.239 524.81% 97.37% 0.68% 1.239 6 38.76% 96.73% 0.81% 49.639 7 42.82% 97.40%0.49% 49.639 8 42.65% 97.53% 0.43% 49.639 8 42.70% 97.44% 0.40% 49.639

Comparative Example 1

Comparative Example 1 demonstrates the dehydrochlorination of2-chloro-1,1,1,2-tetrafluoropropane in the presence of an activatedcarbon catalyst.

An inconel tube (½ inch OD) was filled with 4 cc (1.99 gm) of acidwashed PCB Polynesian coconut shell based carbon from Calgon (6-10mesh). HFC-244bb was fed at 1.04 ml/hour through a vaporizer set at 40°C. using a N₂ sweep of 2.4 sccm (4.0×10⁻⁸ m³) giving a total contacttime of about 32 seconds while controlling the reactor temperature at400° C.

The data in Table 9 show the performance of this process with anactivated carbon catalyst to make HFO-1234yf via HCl elimination overthe period of 15 hours of operation.

TABLE 9 conversion selectivity selectivity Hours of 244bb 1234yf 1233xf1 78% 67%  13% 2 75% 59%  18% 3 68% 56%  22% 4 58% 44%  27% 5 51% 31% 35% 6 46% 15%  39% 7 46% 6% 38% 8 47% 3% 32% 9 45% 2% 29% 10 31% 3% 36%11 21% 5% 64% 12 23% 5% 66% 13 24% 5% 67% 14 24% 6% 73% 15 23% 6% 72%

Note that not all of the activities described above in the generaldescription or the examples are required, that a portion of a specificactivity may not be required, and that one or more further activitiesmay be performed in addition to those described. Still further, theorder in which activities are listed are not necessarily the order inwhich they are performed.

In the foregoing specification, the concepts have been described withreference to specific embodiments. However, one of ordinary skill in theart appreciates that various modifications and changes can be madewithout departing from the scope of the invention as set forth in theclaims below. Accordingly, the specification and figures are to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope ofinvention.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any feature(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature of any or all the claims.

It is to be appreciated that certain features are, for clarity,described herein in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures that are, for brevity, described in the context of a singleembodiment, may also be provided separately or in any subcombination.Further, reference to values stated in ranges include each and everyvalue within that range.

1. A method for producing a fluoropropene of formula CF₃CF═CH₂, comprising: pyrolyzing a hydrofluorochloropropane of formula CF₃CFClCH₃, in the gas-phase in a reaction vessel, maintained at a temperature of from about 400° C. to 700° C., wherein the selectivity for the production of the fluoropropene is at least 80%, in the absence of a catalyst.
 2. The method of claim 1 wherein, said selectivity for the production of said fluoropropene is at least 80% after about 4 hours of continuous operation.
 3. The method of claim 1 wherein, said selectivity for the production of said fluoropropene is at least 80% after about 12 hours of continuous operation.
 4. The method of claim 1, wherein said selectivity for the production of said fluoropropene is at least 85%.
 5. The method of claim 1, wherein said selectivity for the production of said fluoropropene is at least 95%.
 6. The method of claim 1, wherein the said hydrofluorochloropropane is preheated in a vaporizer at a temperature of from about 30° C. to about 100° C.
 7. The method of claim 1, wherein the said hydrofluorochloropropane fed to the reaction vessel further comprises an inert carrier gas.
 8. The method of claim 7 wherein the inert carrier gas is chosen from nitrogen, argon, helium or carbon dioxide.
 9. The method of claim 1, wherein the temperature of the reaction vessel is maintained in the range from about 400° C. to about 600° C.
 10. The method of claim 1, wherein the pressure in the reaction vessel is maintained at a pressure of from 14 psig to 100 psig.
 11. The method of claim 1, wherein the pressure in the reaction vessel is maintained at a pressure of from 40 psig to 85 psig.
 12. The method of claim 1, wherein the pressure in the reaction vessel is maintained at a pressure of from 14 psig to 100 psig and the temperature of the reaction vessel is maintained in the range from about 400° C. to about 500° C. 